Why will redsn0w not recognize my custom IPSW?

[claughton]

I have been having some issues with my iPhone 3G, before I get into those details I have a simpler query.

I have somewhat successfully restored the iPhone using a custom 4.2.1 custom IPSW using Pwnage. I am trying to do a tethered boot using redsn0w and it does not recognize the custom IPSW, is this normal?

I am not sure if this is just something with redsn0w, that it does not handle custom IPSWs? It will recognize the stock 4.2.1 IPSW, but it is my understanding that if I am trying to tethered boot my iPhone, I need to be loading the exact IPSW that is used on the iPhone in question.

Any clarity on this matter would be greatly appreciated.

claughton

[iYeow]

Iphone 3g at 4.2.1 is already untethered jailbreak. Custom firmware or redsn0w will give you untethered jailbreak. You need to put iphone into pwned dfu in order to restore to custom fw.